Update view_charts.py

[Salomon-Mazatlan]

• Word cloud: fetchone() -> fetchall(); all coded segments are now included, not just the first one per code.
• Cumulative case bar charts: missing on in two code_av joins (SQL error with case/file filter).
• case_text joins now use a distinct subquery (12 queries) to avoid duplicated counts.
• Case heatmap: SELECT distinct fid (2 queries), same reason.
• Volume bar/pie charts: ifnull(sum(...), 0) in 12 queries; codes with no codings no longer show as empty rows.
• Hierarchy charts: or counter < 5000 -> and in 4 functions (removes ~5000 idle iterations and possible freezes).
• Minor: missing space in ?and fid.

Note on cases: when a case has several portions assigned from the same file, charts counted each coding once per portion (e.g. 3 codings reported as 6). Fixed with distinct. One historical behavior remains: case-based charts count all codings in the whole file without checking that the segment falls within the portion assigned to the case (pos0-pos1 in case_text); if a case covers only part of a file, counts may include codings outside it. Worth a separate issue.